Find Some Giant Willow Aphids!

Hey Californians, our friends in New Zealand have a problem with Giant Willow Aphids, so they (specifically @stephanie_sopow) are trying to study their predators and parasites in California to see if they can find a potential biocontrol agent. However, they're finding them tough to locate in CA. This is where you come in:

If you see a willow in the next few weeks, check it for aphids and post them to iNat!

These aphids hang out on the stems of willows, and if they're actively feeding, the drop a lot of sugary honeydew that causes a black mold to grow on the ground below them. Look for gray patches on stems (those are the aphids) or black moldy patches on the ground to find them. They're bigger than most aphids, but still smaller than something like a lady beetle. The New Zealanders are particularly interested in a group of wasps in the family Aphidiinae that specialize on parasitizing aphids (!!), so if you see any wasps nearby, or aphids that look like mummies, photograph those too! For more on their project, check out

Anyway, keep an eye out as you explore over the coming weeks. If you're up for the hunt, here's where you can find willows in California:

Oh, and here's what the mold looks like:

And here's what the aphids look like en masse:

Photo: Damon Tighe, CC BY-NC

Posted on 09 November, 2017 05:17 by kueda kueda


Dang. I wish I would have seen this yesterday. I was at this little nature area that has some willows. Saturday I'll be visiting a riparian restoration area that is LOADED with willows. I'll keep an eye out.

Posted by vermfly over 6 years ago

I am up over fifty species of aphids, and have spent quite a bit of time searching willows in Southern California for insects. Never seen one. Since you found one here they can't be completely absent, but they are at least very uncommon here.

Posted by glmory over 6 years ago

Been looking for these guys already. I think I've seen at least 5 species of aphid on willow, but not these.

Posted by silversea_starsong over 6 years ago

Add a Comment

Sign In or Sign Up to add comments